Research On A Lightweight Of Unmanned Sightseeing Vehicle Frame Based On Multi-Objective Optimization

The large amount of tail gas emission from traditional cars will cause irreversible pollution to the atmosphere and aggravate the consumption of oil.Therefore,the research and manufacturing of new energy vehicles was encouraged by state to reduce air pollution and energy consumption.As a combination of driverless driving and new energy vehicle technology,the appearance of unmanned sightseeing vehicles reduces environmental pollution and reduces the incidence of traffic accidents.However,compared with the traditional car,the capability of driving mileage is poor because of its battery pack mass and the vehicle mass is heavier than traditional cars.Due to the existing technical barriers in the battery field,it is particularly important to study the lightweight of unmanned sightseeing vehicles when it is impossible to improve the battery capacity and reduce the weight of power battery pack at the same time.This study takes the frame of unmanned sightseeing vehicle as the research object,and the main research contents are as follows:(1)Solid Works software was used to establish the frame model in order to analyze the overall performance of the frame of the unmanned sightseeing vehicle.The free modal frequency of the frame of the unmanned sightseeing vehicle was analyzed by ANSYS Workbench to determine whether it resonates with the common excitation frequency.The maximum deformation and maximum stress values under four working conditions(full-load bending condition,full-load torsion condition,emergency braking condition and emergency turning condition)were obtained by the statics analysis of the frame of the unmanned sightseeing vehicle,which laid a foundation for the subsequent research on the topology optimization design of the frame.(2)In order to search the optimal material distribution of the frame and optimize the structure layout.The original frame with square plate was replaced by the rectangular steel frame structure to establish the base model of the frame of the unmanned sightseeing vehicle.Then,the mathematical model of the single objective topology optimization of the frame was established and single working condition with topology optimization was carried out to design the frame.In order to design the frame structure satisfying all working conditions at the same time,the multi-condition topology optimization mathematical model was established.The analytic hierarchy process is adopted to determine the weight of each working condition,and the multi-working condition topology optimization was carried out to design the frame.The frame structure was redesigned according to the multi-working condition topology optimization design results,and the finite element analysis of the redesigned frame was carried out to verify the safety performance of the redesigned frame.(3)In order to realize the lightweight design of vehicle frame,a multi-condition and multi-objective optimization design method was proposed.The redesigned frame was taken as the research object while the design variables were selected at first to establish the Kriging approximate model of the frame of the unmanned sightseeing vehicle.Then,the mass of the frame,low order natural frequency value and the maximum stress value of the frame under full load bending condition and full load torsion condition are taken as indexes to establish the mathematical model of multi-condition and multi-objective optimization.Multi-objective genetic algorithm(MOGA)was used to optimize the frame in multi-working conditions and multi-objectives,and the candidate design points were sorted by fuzzy matter-element method and analytic hierarchy process.Compared with the sorting results,the optimal design scheme was selected to complete the lightweight design of the frame of the unmanned sightseeing vehicle.The weight of the frame was reduced by 77.40 kg and the weight was reduced by 6.8%.